SO3 lewis acid/bronsted

[Karen Elrayes 1L]

I'm a little confused with SO3. I know it is a lewis acid because it can accept lone pairs but what kind of bronsted acid/base is it. Because it can accept H+ protons right? So shouldn't it be a bronsted base? Also can it also donate lone pairs and act as a lewis base? I'm confusing myself :(

[Megan Lu 3D]

Hi! To my understanding, SO3 is not a Bronsted acid or base, as it cannot donate or accept a proton. You are right that it is a Lewis acid in water because the sulfur accepts an electron pair, but this electron pair should come from the oxygen atom, not H+ (depicted in the attached image). Perhaps you are thinking of the sulfite ion SO3 (2-), which is a Bronsted base that can accept a proton due to its negative charge?

[Dylan_Nguyen_2C]

I believe SO3 in itself is neither a Bronsted acid nor base because it has no H to donate and cannot accept a bonded hydrogen because of its neutral charge. It can act as a Lewis acid because the central sulfur can accept a lone pair, however not in the form of a bond to hydrogen. It's important to know that just because a compound can act as a Lewis acid or base does not mean it is definitively a bronsted acid or base. Hope this helps